Arrangement for positioning a rotatable driving element relative to a driven gear



March 22, 1966 I G M, BOOT 3,241,386

ARRANGEMENT FOR POSITINING A ROTATABLE DRIVING ELEMENT RELATIVE TO A DRIVEN GEAR Original Filed July 8, 1960 4 Sheets-Sheet 1 G 2 INVENTOR film/P65 M500 7/? BY March 22, 1966 BOOTH ARRANGEMENT FOR POSITIONING A ROTATABLE DRIVING ELEMENT RELATIVE To A DRIVEN GEAR Original Filed July 8. 1960 4 Sheets-Sheet 2 INVENTOR. 650265/7. 5007/7 BY ATTOP/Vfy I March 22, 1966 G. M. BOOTH ARRANGEMENT FOR POSITIONING A ROTATABLE DRIVING ELEMENT RELATIVE TO A DRIVEN GEAR Original Filed July 8, 1960 4 Sheets-Sheet 5 INVENTOR. 650F672 /7 5007' KM aowzm) 4770/P/VEV March 22. 1966 G. M. BOOTH 3,241,336

ARRANGEMENT FOR POSITIONING A ROTATABLE DRIVING ELEMENT RELATIVE TO A DRIVEN GEAR Original Filed July 8, 1960 4 Sheets-Sheet 4.

CENTER L/A/E 0F WORM 6154b? QINVENTOR.

650/965 /7. 5007/, BY Rm 6, MW

United States Patent 3,241,386 ARRANGEMENT FOR POSITIONING A ROTAT- ABLE DRIVING ELEMENT RELATIVE TO A DRIVEN GEAR George M. Booth, Westfield, N .J., assignor to Wallace & Tiernan Inc., a corporation of Delaware Original application July 8, 1960, Ser. No. 41,525, now Patent No. 3,106,105, dated Oct. 8, 1963. Divided and this application Oct. 7, 1963, Ser. No. 314,280

4 Claims. (Cl. 74396) This application is a division of my copending application Serial No. 41,525 filed July 8, 1960, now US. Patent 3,106,105, granted October 8, 1963.

This invention relates to an adjustable reciprocating stroke device. More particularly, this invention relates to an adjustable eccentric or an adjustable reciprocating stroke device capable of substantially infinite adjustment, such as from zero to a given maximum eccentricity. In accordance with one particular embodiment, this invention relates to a positive displacement plunger-type pump employing an adjustable eccentric or adjustable reciproeating stroke device of this invention.

Adjustable eccentrics or adjustable reciprocating stroke devices are well known and have been employed for many purposes. Frequently, however, such devices are not structurally rugged but are mechanically complex and require constant maintenance and attention for satisfactory operation.

It is an object of this invention to provide a simple, rugged, substantially trouble-free adjustable eccentric or adjustable reciprocating stroke device.

It is another object of this invention to provide an adjustable eccentric affording substantially infinite adjustment between zero and a given maximum eccentricity.

It is another object of this invention to provide a positive displacement plunger-type pump employing an adjustable eccentric in accordance with this invention.

Still another object of this invention is to provide an improved positive displacement plunger-type piston pump capable of substantially infinite adjustment in output from zero to a given maximum.

Still another object of this invention is to provide a positive displacement, reciprocating, plunger-type pump, the output of which is capable of variation during operation from zero to a given maximum.

How these and other objects of this invention are achieved will become apparent in the light of the accompanying disclosure made with reference to the accompanying drawings wherein:

FIG. 1 is a plan view in partial cross-section of the adjustable eccentric or adjustable reciprocating stroke device of this invention as disposed in simplex pump arrangement to operate a positive displacement plungeryp p p;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a partial cross-sectional view taken along line 33 of FIG. 2;

FIG. 4 is a plan view of an eccentric bearing, an element of the adjustable eccentric of this invention;

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 2;

FIG. 6 shows perspective views of elements of the adjustable eccentric of this invention and illustrating the principle and operation of this invention;

FIG. 7 is a perspective view of an assembly of elements, adjusting blade and worm gear, and eccentric bearing in dashed outline, further illustrative of this invention;

FIG. 8 is a plan view of a worm-worm gear adjusting element employed in accordance with one feature of this invention;

3,241,386 Patented Mar. 22, 1966 FIG. 9 is an end view of the adjusting element of FIG. 8; and

FIG. 10 is a partial side elevation view of the adjustable eccentric device of this invention.

In accordance with this invention an adjustable eccentric or adjustable reciprocating stroke device is provided in an apparatus comprising a shaft mounted for rotation, a worm fixed to and carried on said shaft, a worm gear meshed with said worm and adapted to be rotated by said worm as said shaft is rotated, an eccentric hearing or plate in contact with and slidably positioned on said worm gear, a blade positioned axially within said worm gear keyed within an opening extending therethrough for axial movement therethrough, said blade extending through an opening provided in said plate for movement therethrough, a key integral with said blade and diagonally positioned on one side or face thereof, said key being positioned within a keyway provided in the opening of said bearing or plate and adapted to slidably move said bearing or plate relative to said worm gear as said blade is moved through said worm gear and said bearing or plate, and means for moving said blade through said worm gear and said hearing or plate. Means are provided in accordance with this invention for adjusting the center distance between a driving means, such as the aforesaid worm, and a driven gear, such as the aforesaid Worm gear, and for adjusting the center of the driving means, such as the center of the Worm, in relation to the center of the face of the driven gear, such as the worm gear.

Referring now to FIGS. 1, 2 and 3 of the drawings which illustrate an embodiment of this invention wherein the adjustable eccentric is employed in simplex pump arrangement, the adjustable eccentric or adjustable reciprocating stroke device of this invention is positioned within housing 30 which is provided with a side cover plate 33 and fitted with upper housing cover 31 fastened to housing 30 by screws 32 passing through flange 31a of cover 31 into tapped holes 30a provided in the upper side of housing 30 as illustrated.

Shaft 12, driven by an electric motor, not shown, extends through housing 30 and has fixed thereto and carries for rotation therewith worm 34. Worm 34 is positioned within housing 30 with respect to and meshed with worm gear 35 so that as shaft 12 rotates and carries with it worm 34, worm gear 35 is rotated about its own center axis. Shaft 12 is fixed and mounted for rotation within ball bearings 36 which are supported by and mounted Within bearing caps fastened to housing 30 and worm gear 35 is journaled in ball bearing 38 fixed and supported by holding ring 37 fastened to the inside of and within the lower portion of housing 30. Worm gear 35 is provided with an opening extending therethrough providing keyways 40 within worm gear 35.

Eccentric bearing or plate 41, shown in greater detail in FIGS. 4 and 5, is slidably positioned on top of worm gear 35 and in contact with the upper surface thereof. As indicated in FIGS. 4 and 5 eccentric bearing 41 is provided with an opening 42 extending therethrough, opening 42 being substantially rectangular in cross-section and carrying on one face or side thereof sloping keyway 44. Eccentric bearing 41 is also provided with two elongated slots 45 extending therethrough Within which are positioned a pair of screws 46 which also pass through plate 48 and engage cooperating tapped holes in worm gear 35, screws 46 passing through slots 45 in eccentric bearing 41. Plate 48 is mounted in contact with and adjacent the upper surface of eccentric bearing 41 and is fastened and fixed to eccentric bearing 41 by means of screws 49 which engage tapped holes 50 provided Within eccentric bearing 41. The diameter of plate 48 is such that it overlays annular groove or flange portion 41a of eccentric bearing 41.

Referring now in detail to FIG. 2 of the drawings, adjusting blade 51 is positioned within the keyway 40 and opening 42 of worm gear and eccentric bearing 41, respectively, and an opening through plate 48. Adjusting blade 51 is substantially rectangular in cross-section and is provided on one side or surface thereof with sloping key 52. The sides or edges of adjusting blade 51 are fitted snugly within keyways of worm gear 35 and Within opening 42 of eccentric bearing 41. Also, sloping keys 52 of adjusting blade 51, fits snuggly within sloping keyway 44 of eccentric bearing 41. Accordingly, the arrangement of adjusting blade 51 within keyways 40 of worm gear 35 and opening 42 and keyway 44 of eccentric bearing 41 can be looked upon as the equivalent of a spline connection inasmuch as adjusting blade 51, although adapted and positioned to be rotated by worm gear 35 in a manner described hereinbelow, is at the same time axially adjustable through worm gear 35 and through eccentric bearing 41 and retaining plate 48 which is fixed to and moves with eccentric bearing 41.

The upper end of adjusting blade 51 is tapered to form threaded shaft portion 54 and is affixed by cooperating nut 55 to be journaled within ball bearing 56 fastened to the lower end of adjusting member 58. Adjusting member 58 extends downwardly through a substantially cylindrical opening 31b provided within the central portion of housing cover 31 and is provided at its lower port-ion with keyway 59. Adjusting member 58 is prevented from turning by pin 60 which extends through an opening provided within the upper portion of housing cover 31 into keyway 59.

Adjusting member 58 at the upper portion thereof is formed into threaded shaft 58a, the upper end of which is threadedly engaged in nut 61 which contains a hollow portion 61a to receive the upper threaded portion 58a of adjusting member 58 as nut 61 is turned to move adjusting member 58 upwardly thereinto. Nut 61 is restrained from axial movement by flange 61b which lies between shoulder 31c at the upper end of housing cover 31 and projecting flange 62a of lower dial housing 62 which is fitted to and closed with upper dial housing cover 62b. Handle 64 is fixed by a set screw 64a to the upper end of nut 61 so that upon turning handle 64, nut 61 is rotated thereby effecting axial movement of adjusting member 58 and axially positioning adjusting blade 51 as desired. Also associated with nut 61 are split clamping parts 65a and 65b. Clamping parts 65a and 65b are forced together by turning handle 66, the other end of handle 66 being threaded engaged to screw 68 which, in cooperation With nut 69, serves to force clamping pieces 65a and 65b against nut 61 to prevent its rotation and thereby fix the position of adjusting member 58 and associated adjusting blade 51 once a setting has been i made by turning handle 64.

As illustrated in the drawings, particularly FIG. 2, eccentric bearing 41 is provided with a peripheral, annular slot or groove 41a into which the downwardly flanged arcuate ends 70a of connecting rod 70 is fitted and positioned. The arcuate end of connecting rod 70 is maintained within annular groove 41a of eccentric bearing 41 by overhanging plate 48. The other end 70b of connecting rod 70 is fastened to wrist pin 71 which engages cross head 72 which, in turn, is fastened to operating plunger 73. Thus, reciprocating motion is brought out of the adjustable eccentric or adjustable reciprocating stroke device of this invention and, as disclosed herein, various sizes and types of plungers 73 can be employed for reciprocation within cylinders of the various types of liquid ends of pumps, feeders or similar apparatus.

Referring now to FIG. 6 of the drawings wherein perspective views of elements of the adjustable eccentric of this invention schematically illustrate the principle and operation of the adjustable eccentric described herein, the

upper view shows the arrangement of Worm gear 35, eccentric bearing 41 and adjusting blade 51 and its key 52 all positioned and arranged (blade 51, worm gear 35 and eccentric bearing 41 being coaxial) for zero eccentricity. As adjusting blade 51 is moved downwardly, such as to the position illustrated in the middle view of FIG. 6 the sloping key 52 forces eccentric bearing 41 to the right, a distance X, as indicated on the drawing, thereby providing a stroke length of 2X. As blade 51 is moved further downwardly within worm gear 35, such as to the position illustrated in the bottom view of FIG. 10, eccentric bearing 41 is moved to the right a maximum distance or eccentricity Y, there by providing a stroke length of 2Y.

FIG. 7 of the drawings is further explanatory of the invention and shows the disposition of adjusting blade 51 within worm gear 35 and keyways 40.

In actual practice only one or two thousandths of an inch clearance is provided between the side edges of adjusting blade 51 and the keyways, particularly the bottoms of keyways 40 in worm gear 35. Adjusting blade 51 is restrained from radial motion within worm gear 35 and eccentric bearing 41 in any and every direction regardless of radial load. It is also pointed out that the width of opening or slot 42 extending through eccentric bearing 41 is held very closely to the thickness of blade 51 with the result that eccentric bearing 41 is rotated exactly in accordance with worm gear 35 and supports the eccentric bearing 41 against radial loads at right angles to the length of the slot. Sloping key 52 on adjusting blade 51 is likewise a good fit in keyway 44 of eccentric bearing 41.

In the operation of the adjustable eccentric or adjustable reciprocating stroke device of this invention an infinite number of eccentricities from zero eccentricity to a given maximum eccentricity is available upon turning handle 64. In the operation of the device of this invention a desired eccentricity or reciprocating stroke length from zero to a given maximum is obtainable by turning handle 64 so as to move adjusting blade 51 downwardly or upwardly within worm gear 35 and eccentric bearing 41. Handle 64 can be turned and blade 51 moved while shaft 12 is rotating and carrying with it Worm 34 which, in turn, meshes with and drives Worm gear '35 which, in turn, causes adjusting blade 51 and eccentric bearing 41 and plate 48 also to be driven or rotated. As handle 64 is turned adjusting blade 51 is moved downwardly or upwardly to the desired position for the desired degree of eccentricity. As adjusting blade 51 is moved downwardly or upwardly within worm gear 35 eccentric bearing 41 is caused to move across the upper face of worm gear 35 responsive to the movement of key 52 within keyway 44 of eccentric bearing 41.

It is pointed out that one of the advantages of the adjustable eccentric of this invention is that relatively high strength is provided with relatively light parts and therefore a minimum of distortion occurs. This advantage is derivable from the fact that the stresses in the several parts or elements of the adjustable eccentric are shear forces rather than bending forces. More particularly, a radial load at right angles to opening or slot 42 of eccentric bearing 41 is carried in shear in adjusting blade 51 at the plane defined by the junction of the upper surface of worm gear 35 with the lower surface of eccentric bearing 41. In all other directions the radial loads are carried partially by adjusting blade 51 in this plane and partially by shear force on key 52 and the edges of adjusting blade 51 in keyways 40 of the Worm gear.

As a special feature of this invention means are provided for readily adjusting the center distance between worm 34 and worm gear 35 as well as for adjusting the center of worm 34 in relation to the center of the concave worm face or the center of curvature of the concave worm face of worm gear 35. Many apparatus, such as the positive displacement plunger-type pumps connected to and operated by the adjustable eccentric device of this invention, require some sort of speed reducer between the prime mover, such as an electric motor, and the driven output element, in the instance of this invention, connecting rod 70. If the speed reducer, in the instance of this invention the combination of elements shaft 12, worm 34 and worm gear 35, has much play in its gearing a more or less violent knock occurs at the time of load reversal. Normal manufacturing tolerances on parts can result in a variation in backlash from a minimum which is required for an oil film to a maximum which results in an objectionable knock.

With respect to this feature of the invention particular reference is made to FIGS. 1, 2 and 8-10 of the drawings. As illustrated therein shaft 12 is carried for rotation within ball bearings 36 which are mounted in bearing caps 80. Bearing caps 80 are fastened to housing 30 on machined faces 81 and have their skirts 80a projecting into clearance holes in housing 30, the clearance being sufficient to be able to slide the bearing caps around for the maximum desired adjustment. The bearing caps 80 are fastened to housing 30 by four screws 82 through clearance holes in the cap itself. Each of the two caps has a vertical slot 84 and a round hole 85.

Two shafts 86 are disposed within housing 30 extending between corresponding slots 84 and holes 85 of bearing caps 80. Shafts 86 have off-center cylindrical ends 87 and screw driver grooves 88 with punched arrow markings 88a at each end. Cylindrical portions 89 of each shaft 86 within housing 30 engage cylindrical holes adjacent to faces '81 and the off-center cylindrical ends 87 engage the round holes 85 or the slots 84 of bearing caps 80. With screws 82 slightly loose adjustment of the center distance between the worm 34 and worm gear 35 is accomplished by rotation of shaft 86 in slots 84, such as by means turning a screw driver inserted in groove 88. As the off-center portion 87 of shaft 86 in slots 84 is rotated the bearing cap 80 rotates about the center of hole 85 thus moving bearing cap 80 either to the right or to the left as seen in FIG. 10. Similarly, rotation of the other eccentric shaft 86 within round holes 85 serves to raise or lower bearing cap 80 in order to adjust the elevation of worm 34 to mesh properly in the concave gear face of worm gear 35. Inasmuch as eccentric rods 86 engage bearing caps 80 on both sides of housing 30 both bearing caps 80 are simultaneously adjusted in like direction and to like extent. Hence, by one adjustment the worm is moved toward or away from the worm gear, i.e., the centerline distance between the worm and worm gear adjusted, and by the other adjustment the worm is moved essentially vertically, i.e., the center of the concave worm face of the worm gear or center of curvature of worm gear face is adjusted relative to the center or centerline of the worm, so that a desired closeness and accuracy of mating of the worm and worm gear are readily achieved and objectionable backlash can be obviated.

Although the invention has been illustrated by embodiments utilizing a worm and worm gear in a reciproaction mechanism, the invention is not limited to such arrangements but may include gear mechanisms for other purposes and utilizing other gear types than worms and Worm gears, wherein it is desired to eliminate meshing backlash in spite of manufacturing variations and tooth wear.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many modifications, substitutions and alterations are possible in the practice of this invention without departing from the spirit or scope thereof.

I claim:

1. Apparatus comprising a shaft mounted for rotation, means for rotating said shaft, a worm fixed on said shaft and adapted to be rotated therewith, a circular worm gear meshed with said worm and adapted to be rotated by said worm as said shaft is rotated, a circular bearing plate in contact with and slidably positioned on top of said worm gear, said bearing plate being provided with a peripheral annular slot in the upper face thereof, a retaining plate fixed to the top of said bearing plate, the pe riphery of said retaining plate extending beyond the inner edge of said slot of said bearing plate, a blade positioned axially with said worm gear keyed within an opening extending therethrough, adapted for vertical movement therein and extending through an opening provided within said bearing plate and said retaining plate, a key integral with said blade and diagonally positioned across one face thereof, said key being positioned within a keyway provided in the opening within said bearing plate and adapted to slidably move said bearing plate together with said retaining plate, relative to the .top of said Worm gear as said blade is moved vertically through said worm gear and said bearing and retaining plates, a connecting rod having one end slidably fitted within the annular slot of said bearing plate, said retaining plate being positioned above the end of said connecting rod in said slot, said end of said connecting rod being disposed within said slot for sliding movement therein whereby any eccentricity between said worm gear and said bearing plate upon rotation of said worm gear and said bearing plate imparts a translational to-and-fro movement to said connecting rod, means for moving said blade vertically through said worm gear and said bearing and eccentric plate and means for adjusting the centerline distance between said worm and said worm gear and between the centerline of said worm and the center of the worm face of said worm gear.

2. Apparatus in accordance with claim 1 wherein said means for adjusting the centerline distance between said worm and said worm gear and between the centerline of said worm and the center of the worm face of said worm gear comprises means for independently, vertically and laterally positioning said shaft carrying said worm relative to said worm gear.

3. Power-transmitting gear apparatus, comprising: a housing frame; a first gear rotatably supported by said frame and rotatable about an axis fixed with reference to said frame; second gear means in meshing relationship with said first gear; a shaft carrying said second gear means; two bearings spaced along said shaft for rotatably supporting the shaft; and means for adjustably supporting said hearings on said frame to permit adjustment of the meshing relationship between said second gear means and said first gear, including means pivotally attaching each of said bearings to said frame about a common pivotal axis parallel to said shaft, said pivotal axis lying in a plane which passes through the rotational axis of said shaft and which is approximately perpendicular to a reference plane defined by said rotational axis and by the shortest line between said rotational axis and the center of rotation of said first gear, a rod member journaJed in said frame also parallel to said shaft and having two similarly off-center cylindrical portions individually engaging the side walls of slots oriented similarly in each of said bearings, means for effecting rotational adjustments of said rod member to cause identical pivotal displacements of both of said bearings with corresponding displacements of said shaft in directions approximately within said reference plane, and means for locking said bearings with respect to said frame to preserve the adjusted positions of said bearings and shaft.

4. Power-transmitting gear apparatus, comprising: a housing frame; a worm gear rotatably supported by said frame and rotatable about an axis fixed with reference to said frame; a worm in meshing relationship with said worm gear; a shaft carrying said worrn; two bearings spaced along said shaft for rotatably supporting the shaft; and means for adjustably supporting said hearings on said frame to permit adjustment of the meshing relationship between said worm and said worm gear, including two rod members each journaled in said frame parallel to said shaft, one of said rod members lying approximately in a reference plane defined by the rotational axis of said shaft and by the shortest line between said rotational axis and the center of rotation of said worm gear, said one rod member having two similarly off-center cylindrical portions individually engaging the side walls of slots similarly oriented vertically in each of said bearings, the other of said rod members lying in a plane passing through said rotational axis of said shaft approximately perpendicular to said reference plane, said other rod member having two similarly off-center cylindrical portions individually engaging the walls of cylindrical holes oriented similarly in each of said bearings, means for effecting rotational adjustments of said one and said other rod members to cause identical displacements of both of said bearings with corresponding displacements of said shaft to effect adjustments respectively of the center distance between said worm and said worm gear and of the center of said worm relative to the face of said worm gear, and means for locking said bearings with respect to said frame to preserve the adjusted positions of said bearings and shaft.

References Cited by the Examiner UNITED STATES PATENTS 1,327,129 1/1920 Wolff 74396 X 1,553,351 9/1925 Wood 74396 2,335,606 11/1943 Pelphrey 74-396 2,347,520 4/1944 Sperry et al 74-396 X 2,573,628 10/1951 Van Duyn 74-398 X 2,748,617 6/1956 Deibel 74398 X 2,972,260 2/1961 Nilges 74396 DON A. WAITE, Primary Examiner. 

1. APPARATUS COMPRISING A SHAFT MOUNTED FOR ROTATION, MEANS FOR ROTATING SAID SHAFT, A WORM FIXED ON SAID SHAFT AND ADAPTED TO BE ROTATED THEREWITH, A CIRCULAR WORM GEAR MESHED WITH SAID WORM AND ADAPTED TO BE ROTATED BY SAID WORM AS SAID SHAFT IS ROTATED, A CIRCULAR BEARING PLATE IN CONTACT WITH SAID SLIDABLY POSITIONED ON TOP OF SAID WORM GEAR, SAID BEARING PLATE BEING PROVIDED WITH A PERIPHERAL ANNULAR SLOT IN THE UPPER FACE THEREOF, A RETAINING PLATE FIXED TO THE TOP OF SAID BEARING PLATE, THE PERIPHERY OF SAID RETAINING PLATE EXTENDING BEYOND THE INNER EDGE OF SAID SLOT OF SAID BEARING PLATE, A BLADE POSITIONED AXIALLY WITH SAID WORM GEAR KEYED WITHIN AN OPENING EXTENDING THERETHROUGH, ADAPTED FOR VERTICAL MOVEMENT THEREIN AND EXTENDING THROUGH AN OPENING PROVIDED WITHIN SAID BEARING PLATE AND SAID RETAINING PLATE, A KEY INTEGRAL WITH SAID BLADE AND DIAGONALLY POSITIONED ACROSS ONE FACE THEREOF, SAID KEY BEING POSITIONED WITHIN A KEYWAY PROVIDED IN THE OPENING WITHIN SAID BEARING PLATE AND ADAPTED TO SLIDABLY MOVE SAID BEARING PLATE TOGETHER WITH SAID RETAINING PLATE, RELATIVE TO THE TOP OF SAID WORM GEAR AS SAID BLADE IS MOVED VERTICALLY THROUGH SAID WORM GEAR AND SAID BEARING AND RETAINING PLATES, A CONNECTING ROD HAVING ONE END SLIDABLY FITTED WITHIN THE ANNULAR SLOT OF SAID BEARING PLATE, SAID RETAINING PLATE BEING POSITIONED ABOVE THE END OF SAID CONNECTING ROD IN SAID SLOT, SAID END OF SAID CONNECTING ROD BEING DISPOSED WITHIN SAID SLOT FOR SLIDING MOVEMENT THEREIN WHEREBY AN ECCENTRICITY BETWEEN SAID WORM GEAR AND SAID BEARING PLATE UPON ROTATION OF SAID WORM GEAR AND SAID BEARING PLATE IMPARTS A TRANSLATIONAL TO-AND-FRO MOVEMENT TO SAID CONNECTING ROD, MEANS FOR MOVING SAID BLADE VERTICALLY THROUGH SAID WORM GEAR AND SAID BEARING AND ECCENTRIC PLATE AND MEANS FOR ADJUSTING THE CENTERLINE DISTANCE BETWEEN SAID WORM AND SAID WORM GEAR AND BETWEEN THE CENTERLINE OF SAID WORM AND THE CENTER OF THE WORM FACE OF SAID WORM GEAR. 